Crystallization Engineering in Aza-Steroid: Application in the Development of Finasteride

Novel and robust crystallization approach based on solid solution formation was developed for the purification of finasteride. This is an unprecedented approach that describes the use of pure finasteride <b>1</b> to purify different lots of finasteride <b>1</b> (impure) contaminated with dihydrofinasteride <b>2</b>

Practical, Asymmetric Route to Sitagliptin and Derivatives: Development and Origin of Diastereoselectivity

The development of a practical and scalable process for the asymmetric synthesis of sitagliptin is reported. Density functional theory calculations reveal that two noncovalent interactions are responsible for the high diastereoselection. The first is an intramolecular hydrogen bond between the enamide NH and the boryl mesylate SO, consistent with MsOH being crucial for high selectivity. The second is a novel C–H···F interaction between the aryl C5-fluoride and the methyl of the mesylate ligand